Christmas cactus? No, it’s actually a Thanksgiving cactus. Photo: Peter coxhead, Wikimedia Commons
As I write this in early November, my “Christmas cactus”—I have five of them—are blooming up a storm. But that’s almost two months before Christmas. That can’t be right! But it is, because these plants—and probably the ones you have at home as well—are not really Christmas cactus. Let me explain.
There is indeed a true Christmas cactus, in fact, two of them (Schlumbergera. × buckleyi and its parent S. russelliana), and they do bloom towards the middle or end of December. But they’re not popular with greenhouse growers who prefer the earlier blooming Thanksgiving cactus or crab cactus (S. truncata), which, as the name suggests, naturally blooms in November, shortly before the American Thanksgiving. So when you buy a Christmas cactus, you actually come home with a Thanksgiving one.
How to Tell the Two Apart
The true Christmas cactus has a distinctly pendent stem, hanging flowers in shades of magenta, and, most obviously, flattened stem segments with smooth, somewhat crenelated edges, but never toothed. And, of course, if your plant naturally blooms at Christmas, that’s another good sign it’s probably the real Christmas cactus.
This plant is generally a pass-along plant, shared between gardeners for generations. It’s rarely sold in nurseries because its long stems shatter too readily, making it difficult to transport.
The Thanksgiving cactus (S. truncata) has stems that grow upright at first, then arch, so it’s more a spreading plant than a distinctly hanging one. Also, its flowers are borne horizontally rather than hanging limply from the stem tip. Most obviously, though, it has distinct teeth on its segments a bit like crab claws, which is why it is also known as crab cactus. Also, unlike the true Christmas cactus, it comes in a wide range of colors: red, fuchsia, magenta, lavender, pink, white, yellow and even orange.
It’s abundantly found in stores of all sorts in the holiday season, even supermarkets. Under normal circumstances, though, it will bloom well before Christmas, in very late October or in November.
But It Was in Bloom at Christmas When I Bought It …
Just to confuse people, Thanksgiving cacti are usually sold in full bloom at Christmas and you may indeed have purchased yours at that season. But now it blooms in November. Why?
Greenhouse growers have learned that if you grow Thanksgiving cactus cool (which saves on heating for them), they can delay its bloom. And if you can do the same in your home, you can encourage your Thanksgiving cactus to bloom for Christmas. Here’s how:
First, both Thanksgiving cactus and the true Christmas cactus need short days (less than 12 hours of sunlight per day) starting in late September or they won’t bloom at all. So, I suggest you put your plants in a spot that receives no artificial light between 6 p.m. and 5:30 a.m. I put mine in the guest room—we never turn on the lights there at night—but you can simply place your plants behind other plants or a piece of furniture: you just have to make sure no artificial light reaches them at night.
Next, you have to keep your Thanksgiving cactus cool, below 60?F (15?C) day and night until just before Christmas. This will slow down the development of its flower buds. Then move the plant into a regularly heated room in mid-December and voilà! Flowers for Christmas!
Or Enjoy the Bloom Whenever It Occurs
Personally, I’ve learned to love flowers whenever they appear. So, I don’t struggle to force my Thanksgiving cactus to bloom for Christmas. If they want to bloom their heads off in November, that’s fine with me. Besides, I do have a real Christmas cactus that will cover the holiday season: it’s always covered in bloom on Christmas Eve. Nor am I upset when both my Christmas cactus and Thanksgiving cactus rebloom in late February or March, which most of them do. Hey, sometimes one will bloom yet again in midsummer, when the days are long (I have no explanation as to why that happens!) and that’s fine with me too.
I say just enjoy the bloom, whenever it occurs. But then, I am a laidback gardener!
Adapted from an article originally published on November 15, 2015.